Generally, miniaturization of semiconductor devices is advancing. A shorter wavelength of light used for lithography contributes to the miniaturization. For example, extreme ultraviolet (EUV: wavelength of 13.5 nm) is known as light used for short wavelength lithography. A reflection type mask is used in EUV lithography. In the reflection type mask, an absorption layer is formed on a reflection layer. When the absorption layer is thick, a shadowing phenomenon occurs during exposure. A reflection layer processed-type mask formed by removing a reflection layer is suggested in order to suppress the shadowing phenomenon. Side walls of the reflection layer are exposed to the outside air in the reflection layer processed-type mask. Therefore, there is a possibility that the reflection layer is oxidized in atmosphere or dissolved by chemicals during cleaning. Coating the side walls of the reflection layer, for example, with a protection film, is effective. However, when the side walls of the reflection layer are coated with the protection film, an effective width of the reflection layer is difficult to measure.